Diagnostic Accuracy of Single-Photon Emission Tomography Ventilation/Perfusion Lung Scan in the Diagnosis of Pulmonary Embolism

Background: Planar ventilation/perfusion ((V) over dot/(Q) over dot) lung scintigraphy is a validated tool for the diagnosis of pulmonary embolism (PE). Nevertheless, given the high rate of nonconclusive (V) over dot/(Q) over dot, further investigation is often necessary. (V) over dot/(Q) over dot single-photon emission CT (SPECT) scan could improve (V) over dot/(Q) over dot performance, but sparse data are available on its accuracy. This study assessed the diagnostic performance of (V) over dot/(Q) over dot SPECT scan in a cohort of consecutive patients with suspected PE. Methods: Three hundred twenty-one consecutive patients with a clinical suspicion of PE were prospectively included. Patients suspected of having PE were managed according to a reference diagnostic strategy validated by a 3-month follow-up. In addition to the reference strategy, patients had a (V) over dot/(Q) over dot SPECT scan, the results of which were compared with the initial work-up results. Results: Prevalence of PE was 0 of 41 (0%; 95% CI, 0%-9%), six of 134 (4%; 95% Cl, 2%-9%), 15 of 36(42%; 95% CI, 27%-58%), and 28 of 32 (88%; 95% CI, 72%-95%) in the normal, low, intermediate, and high (V) over dot/(Q) over dot SPECT scan probability groups, respectively. The combination of (V) over dot/(Q) over dot SPECT scan with clinical probability was diagnostic in 88% of patients. Conclusions: (V) over dot/(Q) over dot SPECT scan results show satisfactory accuracy for PE diagnosis. Validation of dedicated interpretation criteria is required, followed by outcome studies that use (V) over dot/(Q) over dot SPECT scan as part of a diagnostic strategy to rule out PE.